Aerial work apparatus are well known as excellent tools for lifting workers or material to elevated or obstructed locations. Such equipment are provided with an extendible boom which can be rotated on the base to which it is mounted as well as elevated at varying angles to the ground. The boom is typically mounted either to the back of a vehicle or to a self-propelled mobile chassis.
The typical aerial work apparatus will have attached at the outer end of the boom either an aerial platform with which to lift work personnel or a material-handling device such as a winch or forklift with which to lift tools and supplies to and from an elevated work site. Since the choice of device attached to the boom is permanent and not exchangeable, a separate apparatus is therefore needed for each type of lifting operation. In particular, while one aerial lift may be needed to raise material to an elevated work site, a different lift will be required to provide a working platform for those individuals needed to complete the job.
Although a certain amount of material can be carried with the workers in their aerial platform, space and safety considerations limit in most instances the number and size of such items. Moreover, there has been an understandable tendency to avoid placing personnel in the air with a heavy load. This is unfortunate given the fact that the work platform is provided with a control module that allows personnel on the platform to not only control boom angle, boom extension, and boom rotation, but where the boom is mounted on a self-propelled mobile chassis, to also control movement on the ground of the entire apparatus as well. Such control enables the operator on the aerial work platform to achieve close proximity to the work site.
Any aerial work apparatus used for typical material handling operations, on the other hand, can only be controlled by an individual on the ground. The operator often has difficulty maintaining visual contact with the load being lifted or with the drop point for that load because of his distance from the load and/or intervening obstructions. As a result, accurate placement of the material at the desired location will often be subject to guesswork unless the operator is assisted by one or more co-workers spotting for him. Even with spotters, however, control over a load can be a problem when it is being lifted by a winch. Given the tendency of the load to rotate when supported by a single line, there is little an operator can do under those circumstances to keep the load in a desired orientation.
There is a significant need, therefore, for an improved aerial work apparatus that would allow for more accurate lifting and placement of material at work sites. An aerial lift that accomplishes this as well as gives control in the choice of material handling devices to an operator working from an aerial work platform would be even more highly desirable. This invention meets these needs and overcomes other problems and shortcomings in the prior art.